The present invention relates to magnetic system, and more particularly to a method and system for providing magnetic tunneling junctions having improved reliability.
Because of their high magnetoresistanse ratio, spin dependent tunneling sensors, otherwise known as magnetic tunneling junctions (MTJs), are currently of interest for use in a variety of devices, including magnetic memories such as magnetic random access memories (MRAM). FIG. 1 depicts a portion of a conventional magnetic memory, a conventional MRAM 1. The conventional MRAM 1 includes MTJs 10. Each MTJ 10 includes at least a conventional pinned layer 20, a conventional barrier layer 30 and a conventional free layer 40. The conventional barrier layer 30 is typically an insulator that serves as a tunneling barrier between the conventional pinned layer 20 and the conventional fire layer 40. The conventional pinned layer 20 and the conventional free layer 40 are ferromagnetic. The magnetization of the conventional pinned layer 20 is pinned in a particular direction, generally by an antiferromagnetic layer (not shown). The magnetization of the conventional free layer 40 is free to rotate in response to an external field. The conventional MRAM 1 includes a conventional bit line 60 and a conventional bottom lead 50. Current through the MTJ 10 is carried by the conventional bit line 60 and the conventional bottom lead 50.
FIG. 2 is a more detailed diagram of a conventional MTJ 10 and the bottom lead 50. The conventional MTJ 10 includes a conventional seed layer 12 and a conventional antiferromagnetic layer 14. The conventional MTJ 10 shown utilizes a conventional synthetic pinned layer 20. The conventional synthetic pinned layer 20 includes conventional ferromagnetic layers 22 and 26 separated by a nonmagnetic spacer layer 24. The conventional ferromagnetic layers 22 and 26 are antiferromagnetically coupled. The conventional barrier layer 30 is typically Al2O3. In addition, the MTJ 10 typically includes a conventional capping layer 16. The conventional bit line 60 is generally coupled to the conventional capping layer 16. The conventional bottom lead 50, which typically carries a current during reading and writing, is generally composed of Cu or Al. As a result, the conventional bottom lead 50 has a high electrical conductivity, allowing for current to be carried by the conventional bottom lead with little loss.
Although the conventional MRAM 1 and conventional MTJ 10 function, one of ordinary skill in the art will readily recognize that the conventional MTJ 10 may be subject to failure. In particular, conventional barrier layer 30 can be nonuniform. The conventional barrier layer 30 is also typically very thin to allow tunneling of current carriers between the conventional pinned layer 20 and the conventional free layer 40. Because of this nonuniformity, the conventional tunneling barrier 30 is subject to pinholes and other defects which decrease the reliability of the conventional tunneling barrier 30. For example, the current through the conventional tunneling barrier 30 may vary and/or the conventional tunneling barrier 30 may be subject to breakdown. The reliability of the conventional tunneling barrier 30 and, therefore, the reliability of the conventional MTJ 10 are adversely affected.
Accordingly, what is needed is a system and method for providing a more reliable MTJ. The present invention addresses such a need.
The present invention provides a method and system for providing a tunneling junction. The method and system comprise providing a free layer, a pinned layer, and a barrier between the free layer and the pinned layer. The free layer and the pinned layer are ferromagnetic. The barrier layer is an insulator. The magnetic tunneling junction is coupled to an xcex1-Ta lead.
According to the system and method disclosed herein, the present invention provides a magnetic tunneling junction having improved reliability.